Adapt to new Dhall.Map

[jneira]

• Changes to adapt dhall-json to the new incoming dhall-haskell version
• As dhall-json needs the changes of Add IsList instance for Dhall.Map.Map dhall-haskell#624, i've pinned its version in the stack.yaml. Only it will have to change with the new release.

[jneira]

The nix build has failed, as i am on windows dont know if i am able to compute the sha of the dhall-haskell commit to update nix/dhall.nix 🤔

[jneira]

I've added a cabal.project to make it buildable with cabal-2.4.0.0, after the release we should remove the source-repository-package stanza (however i would keep cabal.project)

[Gabriella439]

@jneira: Oh, whoops. I actually already did the work to build against the new Dhall.Map but I forgot to open a pull request for. I can open a pull request with the changes I had in my local repository

[Gabriella439]

Actually, the two branches are close enough that I can just open a pull request against your pull request

[Gabriella439]

@jneira: Alright, I have a pull request open against your branch here: https://github.com/jneira/dhall-json/pull/1

Once you merge that then this pull request will pass

[jneira]

Merged!